sparse_strips/vello_cpu/README.md - external/github.com/linebender/vello - Git at Google

 <div align="center">

 # Vello CPU

 **CPU-based renderer**

 [![Latest published version.](https://img.shields.io/crates/v/vello_cpu.svg)](https://crates.io/crates/vello_cpu)
 [![Documentation build status.](https://img.shields.io/docsrs/vello_cpu.svg)](https://docs.rs/vello_cpu)
 [![Apache 2.0 or MIT license.](https://img.shields.io/badge/license-Apache--2.0_OR_MIT-blue.svg)](#license)
 \
 [![Linebender Zulip chat.](https://img.shields.io/badge/Linebender-%23vello-blue?logo=Zulip)](https://xi.zulipchat.com/#narrow/channel/197075-vello)
 [![GitHub Actions CI status.](https://img.shields.io/github/actions/workflow/status/linebender/vello/ci.yml?logo=github&label=CI)](https://github.com/linebender/vello/actions)
 [![Dependency staleness status.](https://deps.rs/crate/vello_cpu/latest/status.svg)](https://deps.rs/crate/vello_cpu)

 </div>

 <!-- We use cargo-rdme to update the README with the contents of lib.rs.
 To edit the following section, update it in lib.rs, then run:
 cargo rdme --workspace-project=vello_cpu --heading-base-level=0
 Full documentation at https://github.com/orium/cargo-rdme -->

 <!-- Intra-doc links used in lib.rs should be evaluated here.
 See https://linebender.org/blog/doc-include/ for related discussion. -->

 [`RenderContext`]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html
 [RenderContext::set_paint]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.set_paint
 [RenderContext::fill_path]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.fill_path
 [RenderContext::stroke_path]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.stroke_path
 [RenderContext::glyph_run]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.glyph_run
 [`RenderContext::render_to_pixmap`]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.render_to_pixmap
 [`Pixmap`]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.Pixmap.html
 [libm]: https://crates.io/crates/libm

 <!-- cargo-rdme start -->

 Vello CPU is a 2D graphics rendering engine written in Rust, for devices with no or underpowered GPUs.

 We also develop [Vello](https://crates.io/crates/vello), which makes use of the GPU for 2D rendering and has higher performance than Vello CPU.
 Vello CPU is being developed as part of work to address shortcomings in Vello.

 ## Usage

 To use Vello CPU, you need to:

 - Create a [`RenderContext`][], a 2D drawing context for a fixed-size target area.
 - For each object in your scene:
   - Set how the object will be painted, using [`set_paint`][RenderContext::set_paint].
   - Set the shape to be drawn for that object, using methods like [`fill_path`][RenderContext::fill_path],
     [`stroke_path`][RenderContext::stroke_path], or [`glyph_run`][RenderContext::glyph_run].
 - Render it to an image using [`RenderContext::render_to_pixmap`][].

 ```rust
 use vello_cpu::{RenderContext, Pixmap, RenderMode};
 use vello_cpu::{color::{palette::css, PremulRgba8}, kurbo::Rect};
 let width = 10;
 let height = 5;
 let mut context = RenderContext::new(width, height);
 context.set_paint(css::MAGENTA);
 context.fill_rect(&Rect::from_points((3., 1.), (7., 4.)));

 let mut target = Pixmap::new(width, height);
 // While calling `flush` is only strictly necessary if you are rendering using
 // multiple threads, it is recommended to always do this.
 context.flush();
 context.render_to_pixmap(&mut target);

 let expected_render = b"\
     0000000000\
     0001111000\
     0001111000\
     0001111000\
     0000000000";
 let magenta = css::MAGENTA.premultiply().to_rgba8();
 let transparent = PremulRgba8 {r: 0, g: 0, b: 0, a: 0};
 let mut result = Vec::new();
 for pixel in target.data() {
     if *pixel == magenta {
         result.push(b'1');
     } else if *pixel == transparent {
         result.push(b'0');
     } else {
          panic!("Got unexpected pixel value {pixel:?}");
     }
 }
 assert_eq!(&result, expected_render);
 ```

 Feel free to take a look at some further
 [examples](https://github.com/linebender/vello/tree/main/sparse_strips/vello_cpu/examples)
 to better understand how to interact with Vello CPU's API,

 ## Features

 - `std` (enabled by default): Get floating point functions from the standard library
   (likely using your target's libc).
 - `libm`: Use floating point implementations from `libm`.
 - `png`(enabled by default): Allow loading [`Pixmap`]s from PNG images.
   Also required for rendering glyphs with an embedded PNG.
 - `multithreading`: Enable multi-threaded rendering.

 At least one of `std` and `libm` is required; `std` overrides `libm`.

 ## Caveats

 Overall, Vello CPU is already very feature-rich and should be ready for
 production use cases. The main caveat at the moment is that the API is
 still likely to change and not stable yet. For example, we have
 known plans to change the API around how image resources are used.

 Additionally, there are certain APIs that are still very much experimental,
 including for example support for filters. This will be reflected in the
 documentation of those APIs.

 Another caveat is that multi-threading with large thread counts
 (more than 4) might give diminishing returns, especially when
 making heavy use of layers and clip paths.

 ## Performance

 Performance benchmarks can be found [here](https://laurenzv.github.io/vello_chart/),
 As can be seen, Vello CPU achieves compelling performance on both,
 aarch64 and x86 platforms. We also have SIMD optimizations for WASM SIMD,
 meaning that you can expect good performance there as well.

 ## Implementation

 If you want to gain a better understanding of Vello CPU and the
 sparse strips paradigm, you can take a look at the [accompanying
 master's thesis](https://ethz.ch/content/dam/ethz/special-interest/infk/inst-pls/plf-dam/documents/StudentProjects/MasterTheses/2025-Laurenz-Thesis.pdf)
 that was written on the topic. Note that parts of the descriptions might
 become outdated as the implementation changes, but it should give a good
 overview nevertheless.

 <!-- cargo-rdme end -->

 ## Minimum supported Rust Version (MSRV)

 This version of Vello CPU has been verified to compile with **Rust 1.88** and later.

 Future versions of Vello CPU might increase the Rust version requirement.
 It will not be treated as a breaking change and as such can even happen with small patch releases.

 <details>
 <summary>Click here if compiling fails.</summary>

 As time has passed, some of Vello CPU's dependencies could have released versions with a higher Rust requirement.
 If you encounter a compilation issue due to a dependency and don't want to upgrade your Rust toolchain, then you could downgrade the dependency.

 ```sh
 # Use the problematic dependency's name and version
 cargo update -p package_name --precise 0.1.1
 ```

 </details>

 ## Community

 Discussion of Vello CPU development happens in the [Linebender Zulip](https://xi.zulipchat.com/), specifically the [#vello channel](https://xi.zulipchat.com/#narrow/channel/197075-vello).
 All public content can be read without logging in.

 Contributions are welcome by pull request.
 The [Rust code of conduct] applies.

 ## License

 Licensed under either of

 - Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or <http://www.apache.org/licenses/LICENSE-2.0>)
 - MIT license ([LICENSE-MIT](LICENSE-MIT) or <http://opensource.org/licenses/MIT>)

 at your option.

 [Rust code of conduct]: https://www.rust-lang.org/policies/code-of-conduct
	<div align="center">

	# Vello CPU

	CPU-based renderer

	[![Latest published version.](https://img.shields.io/crates/v/vello_cpu.svg)](https://crates.io/crates/vello_cpu)
	[![Documentation build status.](https://img.shields.io/docsrs/vello_cpu.svg)](https://docs.rs/vello_cpu)
	[![Apache 2.0 or MIT license.](https://img.shields.io/badge/license-Apache--2.0_OR_MIT-blue.svg)](#license)
	\
	[![Linebender Zulip chat.](https://img.shields.io/badge/Linebender-%23vello-blue?logo=Zulip)](https://xi.zulipchat.com/#narrow/channel/197075-vello)
	[![GitHub Actions CI status.](https://img.shields.io/github/actions/workflow/status/linebender/vello/ci.yml?logo=github&label=CI)](https://github.com/linebender/vello/actions)
	[![Dependency staleness status.](https://deps.rs/crate/vello_cpu/latest/status.svg)](https://deps.rs/crate/vello_cpu)

	</div>

	<!-- We use cargo-rdme to update the README with the contents of lib.rs.
	To edit the following section, update it in lib.rs, then run:
	cargo rdme --workspace-project=vello_cpu --heading-base-level=0
	Full documentation at https://github.com/orium/cargo-rdme -->

	<!-- Intra-doc links used in lib.rs should be evaluated here.
	See https://linebender.org/blog/doc-include/ for related discussion. -->

	[`RenderContext`]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html
	[RenderContext::set_paint]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.set_paint
	[RenderContext::fill_path]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.fill_path
	[RenderContext::stroke_path]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.stroke_path
	[RenderContext::glyph_run]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.glyph_run
	[`RenderContext::render_to_pixmap`]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.RenderContext.html#method.render_to_pixmap
	[`Pixmap`]: https://docs.rs/vello_cpu/latest/vello_cpu/struct.Pixmap.html
	[libm]: https://crates.io/crates/libm

	<!-- cargo-rdme start -->

	Vello CPU is a 2D graphics rendering engine written in Rust, for devices with no or underpowered GPUs.

	We also develop [Vello](https://crates.io/crates/vello), which makes use of the GPU for 2D rendering and has higher performance than Vello CPU.
	Vello CPU is being developed as part of work to address shortcomings in Vello.

	## Usage

	To use Vello CPU, you need to:

	- Create a [`RenderContext`][], a 2D drawing context for a fixed-size target area.
	- For each object in your scene:
	- Set how the object will be painted, using [`set_paint`][RenderContext::set_paint].
	- Set the shape to be drawn for that object, using methods like [`fill_path`][RenderContext::fill_path],
	[`stroke_path`][RenderContext::stroke_path], or [`glyph_run`][RenderContext::glyph_run].
	- Render it to an image using [`RenderContext::render_to_pixmap`][].

	```rust
	use vello_cpu::{RenderContext, Pixmap, RenderMode};
	use vello_cpu::{color::{palette::css, PremulRgba8}, kurbo::Rect};
	let width = 10;
	let height = 5;
	let mut context = RenderContext::new(width, height);
	context.set_paint(css::MAGENTA);
	context.fill_rect(&Rect::from_points((3., 1.), (7., 4.)));

	let mut target = Pixmap::new(width, height);
	// While calling `flush` is only strictly necessary if you are rendering using
	// multiple threads, it is recommended to always do this.
	context.flush();
	context.render_to_pixmap(&mut target);

	let expected_render = b"\
	0000000000\
	0001111000\
	0001111000\
	0001111000\
	0000000000";
	let magenta = css::MAGENTA.premultiply().to_rgba8();
	let transparent = PremulRgba8 {r: 0, g: 0, b: 0, a: 0};
	let mut result = Vec::new();
	for pixel in target.data() {
	if *pixel == magenta {
	result.push(b'1');
	} else if *pixel == transparent {
	result.push(b'0');
	} else {
	panic!("Got unexpected pixel value {pixel:?}");
	}
	}
	assert_eq!(&result, expected_render);
	```

	Feel free to take a look at some further
	[examples](https://github.com/linebender/vello/tree/main/sparse_strips/vello_cpu/examples)
	to better understand how to interact with Vello CPU's API,

	## Features

	- `std` (enabled by default): Get floating point functions from the standard library
	(likely using your target's libc).
	- `libm`: Use floating point implementations from `libm`.
	- `png`(enabled by default): Allow loading [`Pixmap`]s from PNG images.
	Also required for rendering glyphs with an embedded PNG.
	- `multithreading`: Enable multi-threaded rendering.

	At least one of `std` and `libm` is required; `std` overrides `libm`.

	## Caveats

	Overall, Vello CPU is already very feature-rich and should be ready for
	production use cases. The main caveat at the moment is that the API is
	still likely to change and not stable yet. For example, we have
	known plans to change the API around how image resources are used.

	Additionally, there are certain APIs that are still very much experimental,
	including for example support for filters. This will be reflected in the
	documentation of those APIs.

	Another caveat is that multi-threading with large thread counts
	(more than 4) might give diminishing returns, especially when
	making heavy use of layers and clip paths.

	## Performance

	Performance benchmarks can be found [here](https://laurenzv.github.io/vello_chart/),
	As can be seen, Vello CPU achieves compelling performance on both,
	aarch64 and x86 platforms. We also have SIMD optimizations for WASM SIMD,
	meaning that you can expect good performance there as well.

	## Implementation

	If you want to gain a better understanding of Vello CPU and the
	sparse strips paradigm, you can take a look at the [accompanying
	master's thesis](https://ethz.ch/content/dam/ethz/special-interest/infk/inst-pls/plf-dam/documents/StudentProjects/MasterTheses/2025-Laurenz-Thesis.pdf)
	that was written on the topic. Note that parts of the descriptions might
	become outdated as the implementation changes, but it should give a good
	overview nevertheless.

	<!-- cargo-rdme end -->

	## Minimum supported Rust Version (MSRV)

	This version of Vello CPU has been verified to compile with Rust 1.88 and later.

	Future versions of Vello CPU might increase the Rust version requirement.
	It will not be treated as a breaking change and as such can even happen with small patch releases.

	<details>
	<summary>Click here if compiling fails.</summary>

	As time has passed, some of Vello CPU's dependencies could have released versions with a higher Rust requirement.
	If you encounter a compilation issue due to a dependency and don't want to upgrade your Rust toolchain, then you could downgrade the dependency.

	```sh
	# Use the problematic dependency's name and version
	cargo update -p package_name --precise 0.1.1
	```

	</details>

	## Community

	Discussion of Vello CPU development happens in the [Linebender Zulip](https://xi.zulipchat.com/), specifically the [#vello channel](https://xi.zulipchat.com/#narrow/channel/197075-vello).
	All public content can be read without logging in.

	Contributions are welcome by pull request.
	The [Rust code of conduct] applies.

	## License

	Licensed under either of

	- Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or <http://www.apache.org/licenses/LICENSE-2.0>)
	- MIT license ([LICENSE-MIT](LICENSE-MIT) or <http://opensource.org/licenses/MIT>)

	at your option.

	[Rust code of conduct]: https://www.rust-lang.org/policies/code-of-conduct